20851820 has 24 divisors (see below), whose sum is σ = 47770128. Its totient is φ = 7582400.

The previous prime is 20851801. The next prime is 20851867. The reversal of 20851820 is 2815802.

It is a self number, because there is not a number n which added to its sum of digits gives 20851820.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 47171 + ... + 47610.

It is an arithmetic number, because the mean of its divisors is an integer number (1990422).

Almost surely, 2^20851820 is an apocalyptic number.

20851820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20851820 is an abundant number, since it is smaller than the sum of its proper divisors (26918308).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20851820 is a wasteful number, since it uses less digits than its factorization.

20851820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94801 (or 94799 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 26.

The square root of 20851820 is about 4566.3793096938. The cubic root of 20851820 is about 275.2419688506.

The spelling of 20851820 in words is "twenty million, eight hundred fifty-one thousand, eight hundred twenty".